<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>盒子的外边距如何设置</title>
    <style>
        div {
            /*margin-left: 20px;*/
            /*margin-right: 20px;*/
            /*margin-top: 20px;*/
            width: 200px;
            height: 200px;
            /*简写模式，设置四个简写，也可以写三个，也可以写四个*/
            margin: 20px 12px 18px 23px;

        }
        .my_table{
            border-collapse: collapse;
            width: 500px;
            height: 150px;
        }
        .my_table td,th {
            border: 1px solid black;
            text-align: center;
        }
    </style>
</head>
<body>
<div>
    <table class="my_table">
        <tr>
            <th>*rce</th>
            <th>*erce</th>
            <th>*force</th>
            <th>*source</th>
        </tr>
        <tr>
            <td></td>
            <td>pierce</td>
            <td>force</td>
            <td>source</td>
        </tr>
        <tr>
            <td></td>
            <td>fierce</td>
            <td>enforce</td>
            <td>outsource</td>
        </tr>
    </table>
</div>
</body>
</html>